Lasing modes

Tona, M. Kimura, M., Novel lasing modes observed in a levitated single dye doped micro droplet, J. Rhys. Soc. Jpn 2000, 69, 3533 3535... 

It should be noted, however, that the Q factors of open microcavities do not characterise directly the threshold gain values of the corresponding semiconductor lasers. To overcome this difficulty a new lasing eigenvalue problem (LEP) was introduced recently (Smotrova, 2004). The LEP enables one to quantify accurately the lasing frequencies, thresholds, and near- and far-field patterns separately for various WG modes in semiconductor laser resonators. However, the threshold of a lasing mode depends on other... 

In modem heterostructure lasers, the actual active layer is usually very thin, much thinner than the optical mode to be supported by its optical gain. Therefore, it is convenient to introduce the so-called optical confinement factor T, which relates the material optical gain gmlt to the net optical gain geff seen by the lasing mode [6] ... 

When lasing, nearly every exciton generated above threshold contributes to optical power in the lasing mode, as can be seen by the following relation ... 

The typical setup for the measurement of the fluorescent lifetime (Xf) (Figure 11.5) described in Ref. [25] consisted ofaTiisapphire laser (Spectra-Physics, Tsunami laser pumped by a 10 W Beamlok Ar-ion laser) that was operated in its picosecond lasing mode (1 ps pulses at 82 MHz). The fundamental train of pulses was pulse selected (Spectra-Physics, model 3980) to reduce its repetition rate to typically 0.8-4. MHz... 

Owing to the additional confinement of carriers to within the quantum well structure, the resultant threshold current density becomes considerably less than for bulk double heterostructure devices. Additionally, quantum well lasers generally have a narrower gain spectrum (for similar bias currents to DH structures), a smaller lasing linewidth of the lasing modes, a reduced temperature dependence, and the potential for achieving higher modulation frequencies. 

X. Jiang and C. M. Soukoulis, Localized random lasing modes and a path for observing localization, Phys. Rev. E, 65, 025601-4 (2002). 

The second type of microlaser (Fig. 8b) utilizes a localized state defect mode as a laser cavity (Painter et al., 1999). Here, the localized electromagnetic mode is associated with a missing hole in the 2D triangular lattice. This particular structure has been proposed as the world s smallest microlaser with a cavity volume of 0.03 /xm. Spontaneous emission from electron-hole pair recombination in the multiple quantum well active region occurs preferentially into the localized state. Since the photonic crystal is two-dimensional, spontaneous emission is not exclusive to the lasing mode. This results in a finite pumping threshold before lasing occurs. 

Gaussian state lasing modes Oi,2 we can use a sufficient criterion proposed in Refs. [80], According to the criterion, the two lasing fields are entangled if the sum of the variances of two EPR-like operators u and v of the two modes satisfies the inequality... 

Figure 11 A quantum-beat laser scheme with dynamical noise reduction. Quantum-beat is created by using a microwave field to couple the two closely spaced states 1> and 2). Atoms are pumped incoherently from the ground state 0> to the top state 3) with rate A, emit photons into two lasing modes (ai 2) on the 11,2)- 3> transitions, and then return to the ground state at rate 72.

Nanoscale Optofludic Characterization Techniques, Rgure 4 Nanoscale characterization in a 2D photonic crystal cavity, (a) Resonance mode of a 2D photonic crystal cavity laser calculated using the FDTD method, (b) Red shift of the lasing mode with varying refractive indexes of the surrounding media... 

HPDLCs have periodic refractive index distribution by polymer-rich layer and LC-rich layer, so they can be used as DFB laser cavities. In the DFB laser cavity, the light feedback for lasing modes relies on Bragg scattering by the periodic microstructures [78,79]. The DFB lasing wavelength from the device should satisfy Bragg condition [80]... 

These reports were followed by demonstrations of optically pumped lasing in ZnO [147, 148]. Using an Xe laser, Johnston [147] reported SE at 275 K from ZnO platelets but was unable to explain the data by exdton-LO-phonon theories. Later on, Reynolds et al. [ 149] showed optically pumped lasing in as-grown ZnO platelets using an HeCd laser with very low pump power (4 Wcm ) at 2 K. Extremely well-formed lasing modes were observed from which a changeover from absorption to emission could be clearly detected. 

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